SAN, NAS what's the difference?

[The little lost angel]

I've been reading up on SAN & NAS and getting a little confused.

I've always thought they are different things but it seems like NAS is
just a part of SAN? As in, in a Storage Area Network, basically there
are a whole bunch of machines that are connected normally as well as
having another fibre network just for storage access. The NAS is just
a bunch of drives in a box that's connected to that for access. All
the systems on the storage network can access the NAS directly so
performance is better.

But at the same time, some pages say that a NAS is simply connected to
the Ethernet network and a server controls access to it akin to having
a shared network drive on the server.

Am I badly mistakened about it all or is it just a case of converging
technologies? TIA for any clarification!


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[Curious George]

NAS & SAN are not simply "converging technologies." They fill
different roles/needs.

People use NAS appliances to offload basic file service
responsibilities from existing servers without the large
cost/complexity of additional full-fledged servers. All NAS does is
provide storage via "network share." This simplicity makes it
efficient.

People generally look to SAN to consolidate massive amounts of storage
among many servers. People expect SAN vendors to provide advanced
virtualization software and expect to be able to dynamically change
storage assigned to different servers as roles change or storage is
upgraded. It optimizes usage and management of storage (as opposed to
the many inefficiencies of DAS - "direct attached storage" and with
greater scalability/flexibility than NAS for the largest projects).

Both NAS & SAN can provide storage consolidation the main difference
is SAN uses block level access and NAS uses network file level access.
You look to SAN for massive datacenter type applications and where the
programs that need to access an external storage repository or easily
managed & scaled storage repository require block level access. NAS
products run the gamut of quality/price from free software on a
recycled PC to enterprise devices with advanced features. SAN is
exclusively in the "enterprise" realm.

The group comp.arch.storage has a lot of professionals who
use/administrate/make purchase decisions for SAN & NAS if you want to
continue to ask/learn. SAN & NAS covers a broad range of items with
many different proprietary products and customized installation. The
difference is indeed confusing when talking about these technologies
in the broadest of terms.